DPI scaling is an OS setting. OpenTK has no control over it, but a user can change it using the display settings in the control panel.

In most cases, you should not hardcode windows to a specific pixel size. For example, a 500x500 pixel window will be unusably small on a modern 4K monitor. Instead, you should respect the OS settings and accept that a 500x500 point window may create a 1000x1000 pixel window on system with 200% DPI scaling (e.g. a retina MacBook).

If you must force a specific resolution for some reason, you have two options:
1. Render to a framebuffer object with the desired size. You can then scale to the window size using an interpolation filter of your choice (point, linear or a custom shader.)
2. Disable HiDPI support using: